The M4 platform is/was always a good platform. My preference has been the 8500 series over the 9500 series which I found as "slow" and somewhat unrefined. Doesn't seem like anyone else noticed as it was their best seller.

As long as you have TSR to make the detector more livable in today's K-band infested roadways, you should be good. Not stellar, but good.

Just because a new model comes along that schools everything else, doesn't take away from the performance you are already enjoying, IMO.